Peronospora

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Peronospora
Peronospora manshurica on soybean leaf.jpg
P. manshurica on soybean leaf
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Peronospora

Peronospora is a genus of oomycetes that are obligate plant pathogens of many eudicots.[1] Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamental plants.[2] There are 19 genera that produce downy mildew, and Peronospora has been placed alongside Pseudoperonospora in the group of downy mildews with coloured conidia.[3] Peronospora has far more species than any other genus of the downy mildews.[3] However, many species have been moved from this genus to be reclassified to other or new genera.[4] Among these was the most famous Peronospora species, formerly known as Peronospora parasitica, and now known as Hyaloperonospora parasitica.[4] Now, the Peronospora species of most importance is likely the Peronospora tabacina.[5] Peronospora tabacina causes blue mold on tobacco plants and can severely reduce yields of this economically important crop to the point where it has been classified as a bioweapon.[5][3]

History[edit]

Peronospora was first described in 1837 by August Carl Joseph Corda, a Czech mycologist and physician, in his first of six volumes of his Icones fungorum hucusque cognitorum.[6] Since then, many of the species originally placed in Peronospora have been allocated to other genera or given rise to new genera based on new techniques such as molecular genetics.[4]

There was an epidemic in 1960 of Peronospora tabacina affecting tobacco plants leading to $25 million in losses across eleven countries, which was about 30 percent of the tobacco plants.[5] Another epidemic that was caused by Peronospora destructor reduced the yield of sweet onions by 25 percent in Georgia, USA in 2012, and led to an estimated $18.2 million in losses.[7]

Habitat and ecology[edit]

Most of the Peronospora species are highly specific to their hosts and can generally be found anywhere the host plant grows, or is being cultivated.[3] A large portion of their life cycle in spent inside their host plant. Many species of Peronospora are seedborne pathogens, so the worldwide spread of Peronospora crop-plant pathogens is likely to be a result of unknowingly trading infected seeds to new areas.[3] There are also many Peronospora species that are spread by wind currents, which allows them to disperse over large distances.[3] Peronospora species prefer humid air and cool temperatures.[5]

General form and structure[edit]

The first stage in the Peronospora life history is the sporangia.[5] The sporangia are small spore-like structures about 65 um long that germinate a germ-tube when they are near a leaf stoma.[8][5] A germ tube will come from the sporangium and penetrate the leaf cell where it will form a haustorium.[5] The haustorium absorbs nutrients from the leaf, while hyphae invade the intercellular space, and the leaf will eventually develop a lesion.[5] These lesions often start out yellow and then turn brown as the leaf starts to undergo necrosis.[5] From here, Peronospora can undergo either asexual reproduction or sexual reproduction.[5] Asexual reproduction occurs when the air outside is moist making for favourable conditions.[5] During asexual reproduction, hyphae on the host plant will form sporangiophores, which will produce conidia.[5] The conidia will be dispersed by the wind is able to infect other plants.[5] The asexual cycle only takes five to seven days to complete.[5] Sexual reproduction occurs when the conditions are unfavourable and it needs to withstand harsh environmental conditions.[5] During sexual reproduction, the hyphae will undergo meiosis forming antheridia and oogonia, the only haploid structures in the Peronospora life history.[5] The antheridia will fuse to the oogonia, initiating plasmogamy and then karyogamy, and will result in the production of many oospores.[5] The oospores can then be dispersed by the wind to infect more plants.[5]

Both Peronospora and Pseudoperonospora are characterized by their ability to produce melanized sporangia, but Pseudoperonospora produces zoospores whereas Peronospora cannot.[3]

Practical importance[edit]

The model oomycete pathogen, Peronospora parasitica, used to be included in this genus, however it has been reclassified to the genus Hyaloperonospora.[3]

Some species of Peronospora have been considered for their use as a bioweapon or have been classified as potential bioweapons.[3] Peronspora somniferi was considered for its ability to devastate fields of the opium poppy, which could have targeted areas that depend on the crop.[3] The United States has classified Peronospora tabacina as a possible bioweapon, because if it were used to target the US tobacco industry, it would lead to major economic loss.[3]

Genomics and genetics[edit]

Only one species in the genus Peronospora has had its genome sequenced and assembled. In 2015, Derevnina et al. performed a de novo sequence assembly of the genome of two Peronospora tabacina isolates using Illumina sequencing.[9] They estimated the genome size to be 68 Mb with a mitochondrial genome of 43 kb.[9] The two assemblies had 61.8x and 128.9x coverage for the nuclear genomes and 6,824x and 43,225x coverage for the mitochondrial genomes.[9] The mitochondrial genome only differed by seven single nucleotide polymorphisms, three small indels, and one copy number variant.[9] Using a program to predict gene models, they found 18,000 potential protein coding genes.[9]

List of Peronospora species[edit]

[10]

External links[edit]

References[edit]

  1. ^ Göker, M., García-Blázquez, G., Voglmayr, H., Tellería, M. T., & Martín, M. P. (2009). "Molecular taxonomy of phytopathogenic fungi: a case study in Peronospora". PLOS ONE. 4 (7): e6319. Bibcode:2009PLoSO...4.6319G. doi:10.1371/journal.pone.0006319. PMC 2712678. PMID 19641601.CS1 maint: Multiple names: authors list (link)
  2. ^ Lee, J. S., Shin, H. D., Lee, H. B., & Choi, Y. J. (2017). "Taxonomy and Phylogeny of Peronospora Species (Oomycota) Parasitic to Stellaria and Pseudostellaria in Korea, with the Introduction of Peronospora casparyi sp. nov". Mycobiology. 45 (4): 263–269. doi:10.5941/MYCO.2017.45.4.263. PMC 5780358. PMID 29371794.CS1 maint: Multiple names: authors list (link)
  3. ^ a b c d e f g h i j k Thines, M., & Choi, Y. J. (2015). "Evolution, diversity, and taxonomy of the Peronosporaceae, with focus on the genus Peronospora". Phytopathology. 106 (1): 6–18. doi:10.1094/PHYTO-05-15-0127-RVW. PMID 26649784.CS1 maint: Multiple names: authors list (link)
  4. ^ a b c Göker, M., Voglmayr, H., Riethmüller, A., Weiß, M., & Oberwinkler, F. (2003). "Taxonomic aspects of Peronosporaceae inferred from Bayesian molecular phylogenetics". Canadian Journal of Botany. 81 (7): 672–683. doi:10.1139/b03-066.CS1 maint: Multiple names: authors list (link)
  5. ^ a b c d e f g h i j k l m n o p q r Krsteska, V., Dimeska, V., Stojkov, S., & Stojanoski, P. (2015). "Peronospora tabacina A. the causing agent of Blue Mold disease on tobacco". Bulgarian Journal of Agricultural Science. 21: 132–139.CS1 maint: Multiple names: authors list (link)
  6. ^ Corda, A. C. J. (1837). Icones fungorum hucusque cognitorum, vol. 1.
  7. ^ Parkunan, V., Gitaitis, R. D., Dutta, B., Langston, D. B., & Ji, P. (2013). "An Epidemic of Downy Mildew caused by Peronospora destructor on Vidalia Sweet Onions in Georgia in 2012". Plant Health Progress. 14: 54. doi:10.1094/PHP-2013-0328-01-BR.CS1 maint: Multiple names: authors list (link)
  8. ^ Langston Jr, D. B., & Sumner, D. R. (2000). "First report of downy mildew (caused by Peronospora destructor) of onion in Georgia". Plant Disease. 84 (4): 489. doi:10.1094/PDIS.2000.84.4.489B. PMID 30841183.CS1 maint: Multiple names: authors list (link)
  9. ^ a b c d e Derevnina, L., Chin-Wo-Reyes, S., Martin, F., Wood, K., Froenicke, L., Spring, O., & Michelmore, R. (2015). "Genome sequence and architecture of the tobacco downy mildew pathogen Peronospora tabacina". Molecular Plant-Microbe Interactions. 28 (11): 1198–1215. doi:10.1094/MPMI-05-15-0112-R. PMID 26196322.CS1 maint: Multiple names: authors list (link)
  10. ^ "Taxonomy Browser". www.ncbi.nlm.nih.gov. Retrieved 13 January 2019.